With upsizing of the products using organic EL elements or increase in substrate sizes, a demand for upsizing is also growing with respect to vapor deposition masks. Further, the metal plates for use in production of the vapor deposition masks composed of metals are also upsized. However, with the present metal processing technique, it is difficult to form slits in a large metal plate with high precision and these cannot respond to enhancement in definition of the slits. Further, in the case of use of a vapor deposition mask composed of only a metal, the weight thereof also increases with upsizing, and the total mass including a frame also increases, which becomes a hindrance to handling.
Under such circumstances, in Patent Literature 1, there is proposed a vapor deposition mask including a metal mask in which slits are provided and a resin mask which is positioned on the surface of the metal mask and in which openings corresponding to a pattern to be produced by vapor deposition are arranged for a plurality of rows in the lengthwise direction and the widthwise direction, the metal mask and the resin mask being stacked. The vapor deposition mask proposed in Patent Literature 1 is regarded as being capable of satisfying both high definition and lightweight in upsizing and forming a vapor deposition pattern with high definition.
Moreover, Patent Document 1 above discloses that a cross-sectional shape of the opening or a cross-sectional shape of the slit is preferably a shape having broadening toward a vapor deposition source side in order to prevent generation of a shadow in production by vapor deposition with use of the vapor deposition mask. Notably, the shadow is a phenomenon that a part of a vapor deposition material released from the vapor deposition source collides with inner wall surfaces of the slit of the metal mask and/or the opening of the resin mask and does not reach the vapor deposition target, and thereby, a portion without vapor deposition that has a film thickness smaller than the intended vapor deposition film thickness arises. Furthermore, Patent Literature 1 above discloses that an angle formed by a straight line connecting a lower bottom distal end in the opening of the resin mask and an upper bottom distal end in the opening of the resin mask and the surface of the resin mask is preferably within a range of 5° to 85°, still preferably within a range of 15° to 80°, further preferably within a range of 25° to 65°. Studying the contents of Patent Document 1 above, it can be considered that the cross-sectional shape of the opening is preferably set to be a shape having larger broadening toward the vapor deposition source side in order to effectively prevent generation of a shadow. In other words, it can be considered that an angle formed by the straight line connecting the lower bottom distal end in the opening of the resin mask and the upper bottom distal end in the opening of the resin mask and a surface of the resin mask on a side of not being in contact with the metal mask is preferably set to be as small an angle as possible.
Now, even in the case where the cross-sectional shape of the opening is set to be a shape having broadening toward the vapor deposition source side, when the resin mask has a large thickness, there can be a case where generation of a shadow cannot be sufficiently prevented. Accordingly, it can be considered that in order to sufficiently suppress generation of a shadow, a measure to make the thickness of the resin mask small is needed to be taken while the cross-sectional shape of the opening is set to be a shape having larger broadening toward the vapor deposition source side. However, in the case of taking this measure, the strength of the openings of the resin mask deteriorate, and moreover, the dimensional precision of the openings on the surface of the resin mask not in contact with the metal mask deteriorates. Moreover, as the aforementioned angle formed by the straight line connecting the lower bottom distal end in the opening of the resin mask and the upper bottom distal end in the opening of the resin mask and the surface of the resin mask is made smaller, the opening dimension of the opening on the surface on the side of being in contact with the metal mask becomes larger. In the case where the opening dimension of the opening on the surface of the resin mask on the side of being in contact with the metal mask becomes large, the pitch between the neighboring openings becomes narrow, which can sometimes causes a hindrance in arranging a metal portion for composing a slit of the metal mask between the neighboring openings in the lengthwise direction or the crosswise direction.